diff --git a/include/freetype/freetype.h b/include/freetype/freetype.h
index 8f5755d63..0331240f8 100644
--- a/include/freetype/freetype.h
+++ b/include/freetype/freetype.h
@@ -913,7 +913,8 @@ FT_BEGIN_HEADER
 
     FT_Generic        generic;
 
-    /*# the following are only relevant to scalable outlines */
+    /*# the following are only relevant to scalable outlines; */
+    /*# cf. `FT_Bitmap_Size' for bitmap fonts                 */
     FT_BBox           bbox;
 
     FT_UShort         units_per_EM;